The present inventin relates to a novel process for handling and processing fish meat. More particularly, the present invention is concerned with a process for utilizing fish meat contaminated with sporozoa as normal fish meat by adding a substance which inhibits thiol protease (hereinafter referred to as TPI) to the fish meat contaminated with sporozoa to prevent the development or increase of a jellied condition.
In recent years, the expansion of the fishing grounds and the variation in the fish to be caught have given rise to a new problem, which is a so-called jellied condition in which the fish meat is spottily or wholly softened and liquified due to the development of a jellied condition in certain species of fish. This represents a great problem in the fishery field.
This jellied condition has been heretofore found in tuna and swordfishes in our country. Fish which develop such jellied conditions do not give off any offensive smell and do not exhibit any significant variation in pH. This phenomenon is aparently different from putrefaction. It is known that this phenomenon is ascribable to the parasites of minute sporozoa belonging to the class of protozoa. It is also known that such sporozoa are never parasitic with respect to human beings and are harmless to the human body because there has been no incidence of health problems, even when fish in a jellied condition has been eaten raw.
The jellied fish, although safe and harmless, as described above, cannot be utilized and processed on an economically feasible basis. For example, such jellied condition which occurs in fish, even in a very short period of time after they are caught, detracts greatly from the commercial value of the affected fish. Fish meat is liquified due to the development of a jellied condition and the final product, consisting only of bone and skin, is obtained in the production process of the dried salted fish. When a kneaded meat is prepared from jellied fish meat, the kneaded meat exhibits no gel-forming capability and remains in a curd state after heating. Even when only a small amount of jellied fish is incorporated into kneaded meat from a normal fish, the bonding capability of the meat is lost which results in "neriseihin" having no elasticity, i.e., a poor gel forming capability. Accordingly, jellied fish cannot be used at all for industrial purposes. Also, the fish meat in a jellied condition cannot be used as a filler for a normal kneaded meat. Under these circumstances, fish meat in a jellied condition is useless.
In view of the above described circumstances, we have previously made an epochmaking invention, which produces good processed fish meat from a jellied fish, by adding egg white to the fish to prevent such jellied condition.
However, this process was not fully satisfactory in that the taste and smell of the egg white were imparted to the processed fish meat and it is difficult to cause the egg white to penetrate into the tissue of the fish meat.
As a result of further studies, we have found that after the host has died, the sporozoa produces a proteolytic enzyme which is a thiol type protease and this protease is a direct cause of the jellied condition. We have also found that when a material inhibiting the activity of the thiol type proteolytic enzyme is added to and caused to penetrate into a fish meat contaiminated with sporozoa, the occurrence of jellied condition is effectively prevented without any side effects on the fish meat. These findings form the basis of this invention.